Many communication systems rely on optical fibers for carrying signals, because of the very high bandwidth of optical fibers. In complex systems, it may be desirable to be able to route signals on a particular optical fiber to a given one of a plurality of sources or sinks of optical signals. This could be the case, for example, in a shipboard environment in which communications are accomplished by means of such optical fibers, and the optical fibers themselves, and the sources and sinks of information, are subject to damage due to collision or hostile action. In such an event, it is desirable to be able to disconnect an optical fiber from a failed unit and to reconnect it to an operable unit of the same (or possibly of a different) type.
FIG. 1 represents a prior-art arrangement 10 for routing optical communications fibers among a plurality of sources and sinks of information. In FIG. 1, a first source, sink, or source/sink of optical signals is represented as a box or block 12, and a second source, sink, or source/sink of such signals is represented as a box 14. Similarly, boxes 16 and 18 represent sources/sinks of a particular type of optical communications signals. As illustrated in FIG. 1, an optical fiber 12o carries signals produced by block 12 to a through connector in the form of a bulkhead junction or bulkhead connector 20a of a patch panel 20, and thence through another optical fiber 14o to optical signal source/sink 14. Similarly, optical signals produced by source 18 are carried by an optical fiber 18o to a bulkhead junction or bulkhead connector 20b, and thence by way of an optical fiber 16o to source/sink block 16. Other optical fibers, illustrated together as a bundle 22, extend from various junction connectors, such as exemplary junction connectors 20c, 20d, 20f, and 20g, through a bulkhead holder or wall 24 aperture 26, where they connect to various sources and sinks of optical signal (not illustrated). Junction connectors 20c, 20d, 20f, and 20g connect to various optical fibers 28c, 28d, 28f, and 28g, illustrated together as a bundle 28, which leave the region to connect to various sources and sinks of optical signals.
It will be clear by considering FIG. 1 that the various equipments 12, 14, 16, and 18, as well as the remote equipments, can be connected together in various ways to either bypass damaged or defective equipment, or to apply signals to various different types of processing as may be required or desired, simply by disconnecting a fiber from a junction or patch terminal of patch panel 20, and reconnecting it by way of another junction or patch terminal which communicates with the desired functional block. This ready reconfiguration may be valuable in various contexts.
A disadvantage of the patch-panel routing suggested by FIG. 1 is that troubleshooting is somewhat difficult, in that a problem is usually manifested as a failure of a system including at least a source of optical signals and a sink of optical signals, joined by at least two separate optical fibers and a junction connector. When a failure of such a system is suspected, it is initially not known whether the problem lies in the source, the sink, or the interconnecting optical fibers. The troubleshooting of such arrangements may be done in a multitude of ways. One possible way to troubleshoot a failed system is to divide it into two parts, by disconnecting one of the optical fibers at the bulkhead connector of the junction panel. For example, if the putatively failed system includes source or source/sink 12 and sink or source/sink 14 of FIG. 1, some information could be gleaned by separating optical fiber 14o from bulkhead connector 20a, and placing a light-responsive meter on bulkhead connector 20a. If source 12 is operating, and produces enough light to be displayed on an optical power meter, one may make an initial assumption that source 12 and optical fiber 12o are functional, and the system problem lies elsewhere. If the operating mode of source 12 is not readily controllable, and no light is perceived at bulkhead connector 20a, it may be necessary to disconnect optical fiber 12o from optical source 12, and to substitute a known test light source. With a test light source at the remote end of optical fiber 12o, and an optically responsive meter attached to bulkhead connector 20a, the state of optical fiber 12o can be established without question. Testing of optical fiber path 14o may involve disconnecting optical fiber 14o from bulkhead connector 20a, and applying a light source to the remote side (not visible in FIG. 1) of bulkhead connector 20a, and disconnecting the connection of optical fiber 14o from equipment 14, and placing an optically responsive meter at the near end of fiber 14o. 
While the described testing is tedious but reasonably efficient, the difficulties become greater when the equipments to which the optical fibers are connected lie at remote locations relative to the patch panel 20 of FIG. 1. This would be the case if equipments connected and interacting through optical fiber bundle 22, one or more of bulkhead connectors 20c, 20d, 20e, and or 20f, and optical fiber bundle 28, were to cease to function correctly. In that case, testing would require traveling to at least one of the remote locations to break a connection, and another trip to reestablish the connection. In addition, either the connections and tests would have to be performed seriatim by one person, or the connection/disconnection would have to be coordinated by some form of communications other than the optical fiber in question. In complex systems with hundreds of optical fibers, the testing may result in long down times.
Prior methods for addressing the problems of testing of complex communication systems take forms such as repeater junction boxes, as described in U.S. Pat. No. 6,243,510, issued Jun. 5, 2001 in the name of Rauch, and automatic analysis systems such as that described in U.S. Pat. No. 4,837,856 issued Jun. 6, 1989 in the name of Glista, Jr. In general, the repeater or junction boxes have relatively limited bandwidth, and are complex and expensive, and the automatic analysis arrangements are complex and expensive. The automatic analysis system uses a bypass fiber, and its manufacturing is complex. Another arrangement is described in U.S. Pat. No. 5,793,481, issued Aug. 11, 1998 in the name of Leali, which samples the signals at a location using a splitter/bypass, and processes them to produce an indication of the presence or absence of signals, which is complex.
Improved or alternative arrangements optical fiber status indicators or sensors are desired.